This invention relates to electrical probes that are used with oscilloscopes and other electrical instruments and, more particularly, to an electrical probe having stored probe identification information.
Oscilloscopes, voltmeters and other electrical instruments utilize a probe for sensing waveforms, voltages and the like. The probe is typically a small handheld assembly having an electrical sensing element. The probe is connected by a flexible cable and a connector to the oscilloscope or other instrument. In use, the sensing element is placed in contact with a node in an electrical circuit. A sensed parameter, such as a signal, a voltage or a waveform, is transmitted from the sensing element to the instrument for measurement and/or display.
The probe is detachably connected to the oscilloscope or other electrical instrument. This permits probes with different characteristics to be utilized in different applications. Furthermore, the probe may be removed from the oscilloscope if either the probe or the oscilloscope is malfunctioning. In addition, oscilloscopes typically have two or more channels, and a probe may be moved from one channel to another for various reasons. In general, oscilloscope probes may be frequently connected to and disconnected from oscilloscopes.
Oscilloscope probes of different types and different manufacturers have different parameters, such as capacitance, frequency response and the like. Furthermore, probes of a given model number may have different parameters due to component tolerances and manufacturing variations. In addition, different oscilloscope channels have different characteristics, even if they are intended to be identical, due to component tolerances and manufacturing variations. Accordingly, it is necessary to calibrate a particular combination of oscilloscope probe and oscilloscope channel to obtain high measurement accuracy.
One straightforward approach is to perform a calibration routine each time a probe is connected to the oscilloscope. This ensures accuracy but may be inconvenient and time-consuming if the probe is frequently disconnected from the oscilloscope.
Another approach is to store calibration information for the probe in the probe and to transmit the cation information to the oscilloscope when the probe is connected. This approach has the advantage that the calibration information remains with the probe at all times, but does not take into account the fact that different oscilloscope channels have different characteristics. Accordingly, a probe that is calibrated on one oscilloscope channel may not provide high accuracy measurements when the probe is connected to another channel of the same oscilloscope or to a different oscilloscope. Furthermore, the volume of calibration information may be high, making storage of the information in the probe inconvenient and expensive.
Accordingly, there is a need for improved probe configurations which overcome one or more of the above disadvantages and drawbacks.
According to a first aspect of the invention, an electrical probe is provided for use with an electrical instrument. The probe comprises a probe body, a sensing element affixed to the probe body for sensing an electrical parameter, and a storage device containing probe information that uniquely identifies the probe. The probe further comprises a connector for detachably connecting the probe to the electrical instrument and an electrical circuit for electronically transferring the probe information from the storage device to the electrical instrument. The electrical instrument may comprise an oscilloscope.
The storage device may comprise a read-only memory and preferably comprises an electrically-programmable read-only memory. The probe information contained in the storage device may comprise a model number and a serial number of the probe. The probe information may further comprise probe setup information.
The electrical circuit may comprise means for serially transmitting the probe information from the storage device to the electrical instrument. The probe information may be read from the storage device in response to control signals from the electrical instrument.
According to another aspect of the invention, measurement apparatus includes an electrical instrument and an electrical probe that is detachably connected to the electrical instrument. The probe comprises a probe body, a sensing element for sensing an electrical parameter and a storage device containing probe information that uniquely identifies the probe. The electrical instrument processes the electrical parameter sensed by the sensing element. The electrical instrument comprises means for storing calibration information that is associated with the probe, means for reading the probe information from the storage device in the probe, and means responsive to the probe information for applying the associated calibration information to processing of the electrical parameter. The electrical instrument may comprise an oscilloscope.
According to a further aspect of the invention, a method is provided for calibrating an electrical probe that is detachably connected to an electrical instrument. The method comprises the steps of storing in the probe a probe ID that uniquely identifies the probe, storing in the electrical instrument calibration information that is associated with the probe, electronically transferring the probe ID from the probe to the electrical instrument, using the probe ID to access the associated calibration information, and applying the accessed calibration information to signals measured with the probe.